Sealing devices for preventing the contamination of the bearing grease by debris due to fretting are already known in the prior art. Fretting arises when two stationary metal bodies making contact nevertheless are subject to micro displacements relative to each other. The friction resulting therefrom releases iron powder debris which may contaminate the grease surrounding and lubricating the rolling bodies and the associated rolling tracks of the bearing. It is also known that, when the fretting debris contaminates the grease, the working life of the bearing is negatively affected by it, being reduced significantly. And obviously this absolutely fails to comply with the increasingly stringent specifications of rolling bearings, the specifications being intended to increase the technical and economic value of the product, requiring an increasingly longer working life. Various attempts have been made by the manufacturers of rolling bearings to overcome this drawback. For example, the document EP 1600349 A1 describes a seal mounted on a spacer axially arranged between a radially inner ring of a bearing and an element which generates the axial preload of the the inner ring; the document JP 4338116 B2 describes an anti-fretting device consisting of a polymer spacer inserted between the pair of inner rings of the bearing; the document JP 2008008424 A describes a seal formed by a composite spacer consisting of three components; finally, the document JP 2007292230 A describes a composite spacer. However, the solutions described in the cited documents have a high production cost and in some cases are also difficult to assemble. Moreover, where a polymer spacer is used, the axial play of the bearing becomes uncertain and this is damaging for the working life of the bearing.